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The ___ratelimit() function simply returns zero ("do ratelimiting")
if the trylock fails, but does not adjust the ->missed field. This
means that the resulting dropped printk()s are dropped silently, which
could seriously confuse people trying to do console-log-based debugging.
Therefore, increment the ->missed field upon trylock failure.
Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
79 lines
1.9 KiB
C
79 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* ratelimit.c - Do something with rate limit.
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*
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* Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
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*
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* 2008-05-01 rewrite the function and use a ratelimit_state data struct as
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* parameter. Now every user can use their own standalone ratelimit_state.
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*/
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#include <linux/ratelimit.h>
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#include <linux/jiffies.h>
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#include <linux/export.h>
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/*
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* __ratelimit - rate limiting
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* @rs: ratelimit_state data
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* @func: name of calling function
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*
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* This enforces a rate limit: not more than @rs->burst callbacks
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* in every @rs->interval
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*
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* RETURNS:
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* 0 means callbacks will be suppressed.
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* 1 means go ahead and do it.
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*/
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int ___ratelimit(struct ratelimit_state *rs, const char *func)
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{
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/* Paired with WRITE_ONCE() in .proc_handler().
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* Changing two values seperately could be inconsistent
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* and some message could be lost. (See: net_ratelimit_state).
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*/
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int interval = READ_ONCE(rs->interval);
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int burst = READ_ONCE(rs->burst);
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unsigned long flags;
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int ret;
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if (!interval)
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return 1;
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/*
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* If we contend on this state's lock then almost
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* by definition we are too busy to print a message,
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* in addition to the one that will be printed by
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* the entity that is holding the lock already:
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*/
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if (!raw_spin_trylock_irqsave(&rs->lock, flags)) {
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ratelimit_state_inc_miss(rs);
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return 0;
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}
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if (!rs->begin)
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rs->begin = jiffies;
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if (time_is_before_jiffies(rs->begin + interval)) {
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int m = ratelimit_state_reset_miss(rs);
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if (m) {
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if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
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printk_deferred(KERN_WARNING
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"%s: %d callbacks suppressed\n", func, m);
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}
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}
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rs->begin = jiffies;
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rs->printed = 0;
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}
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if (burst && burst > rs->printed) {
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rs->printed++;
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ret = 1;
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} else {
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ratelimit_state_inc_miss(rs);
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ret = 0;
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}
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raw_spin_unlock_irqrestore(&rs->lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(___ratelimit);
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